=The North Choir Aisle= and the two aisles which adjoin it were lengthened one bay by the gradual inclusion of the eastern aisle of the transept. A heavy pier has been left with no attempt at decoration on the transept side but with a cluster of shafts on the side facing east; and the next pier to the north has been similarly treated. It will be noticed that the arches over these western bays of the north choir aisle and Lady Chapel, being the arches of the old transept aisle, are extremely massive; unlike anything else in the church, except the one remaining arch, is the corresponding south transept aisle (now St. Lucy's Chapel): these are therefore thought to be unrestored parts of Ethelred's works. The fact that Norman vaulting shafts have evidently been inserted into the pier walls of the aisles point also to the conclusion that the aisle was erected at a date when vaulting shafts were not in use. At the east end there is a small arch, extremely rough, its ragstone voussoirs patched in one part with a block of modern stone. A similar arch is to be seen in the wall of the next (Lady) Chapel, and between these two are traces of another. These three arches led to one of the most interesting architectural discoveries of recent years; and one can hardly look at them unmoved, remembering that they form part of the original church which was built by St. Frideswide and her father. They were indeed the three "chancel arches" (if one may use the expression) which led into the three apses, the discovery of which we have described in our chapter on the exterior of the cathedral.